Rescue workers have pulled several children alive out of the rubble of the schools.

The severe weather outbreak was expected to spread across other parts of the Plains and the Midwest. An earlier tornado killed two people in Oklahoma Sunday.

The National Weather Service placed parts of five storm-battered states -- Oklahoma, Kansas, Missouri, Arkansas and Texas -- under a tornado watch, meaning conditions are favorable for tornadoes to develop.

The same suburb of Oklahoma City was hit hard by a tornado in 1999. That storm had the highest winds ever recorded near the Earth's surface.